12 MASS. EXPERIMENT STATION BULLETIN 203 



corn and burkwhcat in single-salt solutions. Also the ameliorating effects of 

 Ca, K, 01 1 and Mg ions in separate cultures are noted. 



Majinesiuni Requirement of Crops. (A. B. Beaumont and M. E. Snell.) 

 The crops grown in the field in 1932 were alsike clover, buckwheat, soy beans, corn, 

 and oats. Oats on magnesium-deficient plots exhibited a marked chlorosis of 

 intervenous leaf tissue in the early stages of growth, but lost this sympton in later 

 stages. Buckwheat and corn developed mottled chlorotic leaves in the late- 

 growth stages. Only in case of buckwheat was the yield better on plots which 

 received magesium sulfate than on magnesium-deficient plots. 



Top-dressing Grasslands with Fertilizers. (A. B. Beaumont and M. E. Snell.) 



Fertilizer ratios. This experiment was expanded in 1932 to include a wider 

 range of ratios. In both the old and the new portions of the experiment the results 

 show a definite response to increments of potash only. The highest yield was from 

 fertilizer having a ratio of 3:3:8 (N:P205:K20). High nitrogen failed to rank 

 as high as in the past four years, probably because a second cutting could not be 

 made on account of the drought of the latter part of the summer. 



Forms of nitrogen. In a new experiment in the top-dressing of an old mowing 

 (meadow) with different commercial forms of nitrogen, the highest yield was ob- 

 tained from nitrate of soda, followed by ammonium sulfate, urea, and calcium 

 cyanamid in order. Here, again, on account of dry weather no second cutting 

 was available, and this may have affected the order of the results. 



Assimilation of Fixed Nitrogen by Grasses and Clovers. (A. B. Beaumont, 

 W. S. Eisenmenger and W. J. Moore.) Five species of grasses and clovers used for 

 forage were grown in sterilized and unsterilized solution cultures which contained 

 sodium nitrate, ammonium sulfate, or urea in addition to the requisite minerals. 

 From the weight of dry matter produced and from the chemical composition, it 

 was conclufled that nitrogen was assimilated most completely in the fcrm of 

 nitrate by the grasses, and in the form of urea by the clovers. In the later stages 

 of growth, ammonium sulfate and urea became toxic to both grasses and clover. 

 In the unsterilized cultures the roots became dark and decayed, but in the sterilized 

 cultures they remained white and sound. In explanation of the darkening and 

 decay of the roots, the narrowing of the C-N ratio by the accumulation of unas- 

 similated nitrogen in the roots is suggested. The addition of calcium carbonate 

 to the ammonium sulfate solution maintained the reaction near the neutral point, 

 but this did not prevent the injurious action on the roots, nor did it materially 

 increase the growth of the plant and the assimilation of nitrogen. 



Nitrification of Castor Pomace, Soy Bean Meal, and Other Organic 

 Materials. (M. H. Cubbon.) Nitrate nitrogen accumulation in an acid soil of 

 low fertility as influenced by the above materials was studied in the laboratory 

 over a three-month period. Readings were taken at 10-day intervals. The nitro- 

 gen content of the castor pomace samples varied from 4.36 to 5.80 per cent. In 

 three months' time 75 to 100 per cent of the nitrogen in castor pomace and soy 

 bean meal was nitrified. High oil content (10.24 per cent in castor pomace and 

 18.62 per cent in soy bean meal) slightly hindered but did not prevent nitrate 

 accumulation. Nearly half the nitrogen in such organic materials as peanut shell 

 meal, garbage tankage, ground peat, "soil sponge," and "hyper humus" changed 

 to nitrate in three months. Peanut shell meal caused a decided depression of 

 nitrates for the first month. Nitrate accumulation from sulfate of ammonia 

 proceeded at average level after the first month. Apparently a month is necessary 

 in this soil for nitrate accumulation to be noticeable. 



